一般来说对于合同的小修改，没有必要重新签订合同，重新签订都是费时费力，也没有必要，所以都用补充协议对原合同进行修改。如果对合同改变重大的话，比如对方想换个姊妹公司来签合同，或者合同条款有多处重大变更，可以说从根本上改变了合同的内容，都可以重新签订合同的。重新签订合同有两种方式。一种是交出所有原合同的原件，然后废除，撕毁都可以，然后再签订新合同；
如果对合同原件到底有多少份不清楚的话，保险起见可以先起草一个对原合同的终止协议，然后再签新合同。当然如果为了做到天衣无缝，两个合同之间权责无缝转移的话，我自己使用过这种模式，不用撕毁原合同或者起草终止协议，先在新合同中写终止原合同，一般写新合同生效后原合同立即终止，在新合同未生效前原合同保持有效。然后在新合同上盖上三种章，第一种是原合同的对方的章，第二种是新合同的对方的章，第三种是我方的章，这样操作有个缺点是财务看见合同上有三个章，如果她们不看合同内容的话，有时候容易混淆合同内容。
言归正传，给大家分享一个我起草的比较简单的补充协议。
忘了给大家说了，之前跟一位做国际工程的朋友讨论补充协议和变更怎么翻译，我倾向于合同变更翻译为amendment, 补充协议翻译为addendum.不知道大家什麽意见？不过我自己一般都是不加区分的用amendment的。
EXPLOSIVES SALE AGREEMENT
Amendment to the Contract Agreement
Between
The XXX COMPANY
and
MULTI BIZ FZE
WHEREAS: The Explosives Sale Agreement with Contract No: XXX for the construction of XYZ Motorway Road Project has been signed on 11 March 20xx between XXX Company(hereinafter called "the Buyer") and the MULTI BIZ FZE(hereinafter called "the Seller").
评注:先说我们什么什么时候签订了一个合同。
WHEREAS: The Buyer and the Seller have a meeting about the L/C and the Contract Agreement in the afternoon of 25 March 20xx, the Seller suggested that the volume of the goods is excessive and deliver them in one time would be hard; the Seller further suggested that the transshipment would not affect the goods quality since the goods are loaded with containers in the whole shipping period, it is very normal for cargoes to be transshipped in international shipment.
评注：再说这个合同要修改，为什么原因修改，也可以把谈判的过程加上。
IT IS HEREBY AGREED as follows:
评注：双方都同意如下。
In order to ensure the smooth execution of the said Contract Agreement, it is agreed that the goods should be allow to transshipped and partial shipped; accordingly, delete the word "not" from second line, first paragraph of Clause 14 shipment of the Contract agreement (Contract No. CCCAAA-MBIZ-01-20xx).
The Seller further agreed that the goods would all be delivered within two shipments.
评注：上面就是要修改的内容了。
For any discrepancy between this amendment and any of the Contract Agreement, both parties agreed that this amendment to the Contract Agreement shall prevail.
评注：如果这个补充协议和之前签订的合同有冲突，那么以这个补充协议为准，一般可以不写这一句，因为法律上规定一般是后面的文件有效，不过为了避免争议，也为了保险起见，我个人喜欢加上这一句。
IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed the day and year first before written.
On behalf of the Seller
Position___________________________
Name____________________________
Signature__________________________
Date____________________________
Tel____________________________
On behalf of the Buyer
Position___________________________
Name____________________________
Signature__________________________
Date____________________________
Tel____________________________
Witnesses
Name____________________________
Signature____________________________